spring设置字符编码过滤器

一、在web.xml中的配置

    <!-- characterEncodingFilter字符编码过滤器 -->
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <!--要使用的字符集，一般我们使用UTF-8(保险起见UTF-8最好)-->
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
            <!--是否强制设置request的编码为encoding，默认false，不建议更改-->
            <param-name>forceRequestEncoding</param-name>
            <param-value>false</param-value>
        </init-param>
        <init-param>
            <!--是否强制设置response的编码为encoding，建议设置为true，下面有关于这个参数的解释-->
            <param-name>forceResponseEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <!--这里不能留空或者直接写 ' / ' ，否者不起作用-->
        <url-pattern>/*</url-pattern>
    </filter-mapping>

二、CharacterEncodingFilter过滤器类浅析

打开该类源码，可以看到该类有三个类属性

private String encoding; //要使用的字符集，一般我们使用UTF-8(保险起见UTF-8最好)
private boolean forceRequestEncoding = false; //是否强制设置request的编码为encoding
private boolean forceResponseEncoding = false; //是否强制设置response的编码为encoding

主要方法只有一个，也就是下面这个，代码逻辑很简单，入注释所解释

 @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {

        String encoding = getEncoding();
        if (encoding != null) { //如果设置了encoding的值，则根据情况设置request和response的编码
            //若设置request强制编码或request本身就没有设置编码
            //则设置编码为encoding表示的值
            if (isForceRequestEncoding() || request.getCharacterEncoding() == null) {
                request.setCharacterEncoding(encoding);
            }
            //若设置response强制编码，则设置编码为encoding表示的值
            if (isForceResponseEncoding()) { //请注意这行代码，下面有额外提醒
                response.setCharacterEncoding(encoding);
            }
        }
        filterChain.doFilter(request, response);
    }

# 额外提醒

if (isForceResponseEncoding()) {
    response.setCharacterEncoding(encoding);
}

是在

filterChain.doFilter(request, response);
之前执行的，这也就是说这段代码的作用是设置response的默认编码方式，在之后的代码里是可以根据需求设置为其他编码的，即这里设置的编码可能不是最终的编码

对于get请求中文参数出现乱码解决方法有两个：

修改tomcat配置文件添加编码与工程编码一致，如下：

<Connector URIEncoding="utf-8" connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443"/>

另外一种方法对参数进行重新编码：

String userName = new String(request.getParamter("userName").getBytes("ISO8859-1"),"utf-8")

ISO8859-1是tomcat默认编码，需要将tomcat编码后的内容按utf-8编码

三、可以自定义拦截器（在web.xml中配置)

 <filter>
    <filter-name>SetCharacterEncodingFilter</filter-name>
    <filter-class>com.itwang.filter.SetCharacterEncodingFilter</filter-class>
      <init-param>
          <param-name>encoding</param-name>
          <param-value>UTF-8</param-value>
      </init-param>
  </filter>
  <filter-mapping>
    <filter-name>SetCharacterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

public class SetCharacterEncodingFilter implements Filter {

    private FilterConfig filterConfig;

    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }

    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest  request;
        HttpServletResponse response;
        try {
            request = (HttpServletRequest) req;
            response = (HttpServletResponse) res;
        } catch (ClassCastException e) {
            throw new ServletException("non-HTTP request or response");
        }

        String encoding = filterConfig.getInitParameter("encoding");
        if(encoding==null){
            encoding = "UTF-8";
        }

        //POST:
        request.setCharacterEncoding(encoding);
        response.setCharacterEncoding(encoding);
        response.setContentType("text/html;charset="+encoding);
        chain.doFilter(request, response);
    }

    public void destroy() {

    }

}

参考：https://blog.csdn.net/lianjunzongsiling/article/details/77926370